Fuel oil composition



United States Patent 3,458,296 FUEL OIL COMPOSITION Gordon G. Knapp,Southfield, and Joseph P. Klelman, Royal Oak, Mich., assignors to EthylCorporation, New York, N.Y., a corporation of Virginia No Drawing. FiledDec. 7, 1966, Ser. No. 599,713 Int. Cl. C101 1/18; C06b 15/00 U.S. Cl.44-66 7 Claims ABSTRACT OF THE DISCLOSURE A fuel oil composition havingimproved cold flow containing from about 0.04 to about 0.5 percent byweight of an ester of palmitic acid and an anhydroalkitol. Ananhydroalkitol is a cyclic ether product obtained from intramoleculardehydration of polyhydroxy alcohols having 5 or 6 carbon atoms. Thepalmitates of anhydrosorbitol are preferred esters.

Background of the invention Residual and distillate petroleumhydrocarbons are used as fuels in various applications. They are used asdiesel fuels, jet fuels, home heating fuel, turbine fuels, rocket fuels,and in similar combustion systems. It is recognized that the fluidity offuel oils in general is reduced as they are cooled. Additives whichreduce the tendency of these fuels to become more viscous at lowtemperatures are available and are called pour point depressants.Another phenomenon which occurs when these fuels are cooled is thatorifices and other narrow openings through which the fuel passes tend tobecome plugged. This occurs even when the fuel oil contains pour pointdepressants adequate to mantain proper viscosity at low temperatures.This latter characteristic of fuel oils, that is, their ability to flowthrough narrow orifices at low temperatures is referred to as cold flow.

In view of this ned to overcome orifice plugging at low temperatures,additives which function as cold flow improvers in fuel oils are ofsubstantial importance. As stated above, this invention comprises thediscovery that certain esters of palmitic acid and anhydroalkitols areeffective cold flow improvers in hydrocarbon fuel oils,

Summary of the invention This invention relates to hydrocarbon fuel oilcompositions having improved cold flow. It more particularly relates tofuel oil compositions containing esters of palmitic acid and ananhydroalkitol, said alkitol having from 5 to 7 carbon atoms. Apreferred embodiment relates to a method for improving the cold flowcharacteristics of a fuel oil by adding thereto a small amount of anester of palmitic acid and an anhydrosorbitol.

It is an object of this invention to provide a fuel oil having improvedcold flow properties. It is a further object of this invention toprovide a fuel oil containing a small amount of an ester of palmiticacid and a C to C anhydroalkitol sufficient to improve the cold flowcharacteristics of the fuel. Still another object of this invention isto provide a method for improving the cold flow characteristics of afuel oil by adding thereto a small quantity of an ester of palmitic acidand a C to C anhydroalkitol. These and other objects of the inventionwill be made clear' from the'description and claims which follow.

Description of the preferred embodiments An embodiment of this inventionis a fuel oil having improved cold flow characteristics containing from0.04 to about 0.5 percent by weight of an ester of palmitic acid and ananhydroalkitol, said anhydroalkitol having 5 to 7 carbon atoms. Apreferred embodiment of this invention is the fuel oil described abovewherein the ester is present at a concentration of about 0.06 to about0.1 percent by weight, A more preferred embodiment of this invention isthe fuel oil described above wherein the ester is selected from thegroup consisting of sorbitan monopalmitate, sorbide monopalmitate,sorbitan dipalmitate, sorbide dipalmitate, and mixtures thereof. Stillmore preferred embodiments of this invention are fuel oils describedabove wherein the ester is sorbitan palmitate; and fuel oils describedabove wherein the ester is sorbitan dipalmitate. A most preferredembodiment of this invention is a fuel oil as described above whereinthe ester is sorbide monopalmitate or sorbide dipalmitate.

The fuels which are used in the compositions of this invention arepetroleum hydrocarbons. They may be distillate fuels, residual fuels orblends of these two types. The distillate fuels are fractionation cutsfrom the distillation of either crude oil or the products from acracking process. Cracked distillates are usually blended with straightrun distillates before using. Kerosene is a typical distillate fuel. Aresidual fuel oil is the viscous product left after the more volatilefractions have been distilled or topped from the crude oil. It is theleast expensive of the fuels obtainable from petroleum. -It is usedalone as well as in blends with the lower boiling distillate fuelfractions.

These fuels are also characterized by their boiling point range. Ingeneral, the useful fuels have a boiling point ranging from about F. toabout 1,000 P, The boiling point on most commonly used fuels ranges fromabout 200 F. to about 800 Useful fuels include diesel fuel oil gradeDFA, DF-l, DF- 2; domestic fuel oils Nos. 1, 2, 3, 4 and 5; jet fuelssuch as JP-l, LIP-4, JP-S, and the like.

The cold flow improver compounds which are used in the fuel compositionsin the present invention are esters of palmitic acid and C to Canhydroalkitols. An anhydroalkitol is an intramolecular dehydrogenationproduct of an alkitol. The term alkitol means a polyhydric alcoholhaving at least 4 carbon atoms and at least 4 hydroxyl groups. Examplesof suitable alkitols are mannitol, dulcitol, xylitol, and the like. Amost preferred alkitol is sorbitol.

The alkitols are readily dehydrated to form cyclic ether type compounds.When one molecule of water is lost from an alkitol by intramoleculardehydration, a polyhydric monocyclic ether is produced. The generic namefor such a compound is an alkitan. When two molecules of water areremoved from an alkitol by intra-molecular dehydration, a polyhydricdicyclic ether is produced. The term alkide is applied to this product.Thus, for example, if dulcitol were dehydrated, the product obtained onremoving one molecule of water would be termed dulcitan; if twomolecules of water were removed, the product would be termed dulcide.

Anhydroalkitols which are preferred are the products obtained byintramolecular dehydration of sorbitol. When one molecule of water isthus removed, the prodnot is sorbitan; when two molecules of water arethus removed, the product is sorbide.

Esters which are suitable for the purpose of this invention are thoseobtained by reacting the alkitans and alkides described above withpalmitic acid. Palmitic acid is a 16 carbon saturated monocarboxylicacid. It is commonly obtained by hydrolyzing palm oil and separating itfrom the mixed product; the acid can also be made synthetically, as forexample, by carbonylating a suitable olefin in the presence of water.

The esters which are useful in the present invention include themonoesters, the diesters and mixtures thereof. Monoesters are those inwhich one hydroxyl group in the alkitan or alkide is esterified.Examples of useful monoesters are dulcitan monopalmitate, maunidemonopalmitate, adonitan monopalmitate, and the like. Preferredmonoesters are sorbide monopalmitate and sorbitan monopalmitate.

Diesters are obtained when two hydroxyl groups are esterified. Usefuldiesters are mannitan dipalmitate, xylitan dipalmitate and dulcidedipalmitate. Diesters which are preferred are sorbitan dipalmitate andsorbide dipalmitate.

Mixtures of these alkide and alkitan esters are also useful. Thus, forexample, mixtures of mannitan monoand dipalmitate; sorbide monopalmitateand dipalmitate; dulcitan monopalmitate and dulcide monopalmitate;sorbide dipalmitate and sorbitan dipalmitate; mannide monopalmitate andsorbide monopalmitate, and the like are useful in the compositions ofthis invention.

These ester mixtures may also include the alkide and alkitan esters ofother fatty acids. Thus, for example, sorbide or sorbitan may beesterified with the mixed acids obtained from palm oil. A typicalcomposition of fatty acids obtained from palm oil is 42 /2 percentpalmitic acid, 43 percent oleic acid, with the remainder being myristic,stearic and linoleic acid. Using this mixture of acids, the sorbitan orsorbide ester product will contain analagous quantities of the variousesters, that is, palmitates, myristates, oleates, stearates andlinoleates. Such ester mixtures are useful in the practice of thisinvention. When making up the fuel oil compositions, sufficientquantities of the mixed ester would be used in order that theconcentration of palmitate esters is within the weight range disclosedabove. The mixed acids may also be those obtained from commercialsynthesis processes such as from Ziegler catalyzed chain growthprocedures. On the other hand, the mixed acids may be purposely blendedfor economic reasons and then used to esterify alkitans and alkides. Ingeneral then, mixed esters containing other carboxylic alkyl residuesbesides palmitate may be used in the practice of this invention.

The anhydroalkitol esters which are used in the present invention arewell known compounds. Methods for their preparation are given in theliterature. Procedures for their preparation are presented in U.S.2,322,820 and U.S. 2,398,193. The procedures described in these patentsare conveniently used to make esters used in the present invention.

The following examples illustrate typical ester preparations. All partsare by weight unless otherwise specified.

Example 1 A mixture of 52 parts of sorbitol syrup and 102.6 parts ofpalmitic acid and about 0.1 part of 85 percent phosphoric acid wereheated to 200 F. in a suitable vessel with stirring in a nitrogenatmosphere. The temperature of the mixture was maintained between 200and 250 C. until no more water came off. (Small amounts of toluene wereadded to the reaction mixture to prevent palmitic acid from clogging thecondenser and to azeotrope the water.) When all of the water wasremoved, the reaction mixture was cooled. The product was dissolved inpetroleum ether and recrystallized. The yield was 120 parts of sorbidedipalmitate.

Example 2 To a reaction vessel fitted with condenser, inlet tube andstirrer are added 260 parts of sorbitol syrup (70 percent sorbitol),about 2 parts of sodium hydroxide, and 256 parts of palmitic acid. Themixture is stirred and heated at 220 to 240 C. Water of reaction isconstantly being removed. The dehydration and esterification arecomplete after 4 hours. The product obtained is sorbitan monopalrnitate.

The quantity of e'ster which is used to prepare the improved fuelcompositions of the present invention may be from 0.04 to about 0.5percent by weight of the fuel oil. The preferred range is 0.05 to about0.1 percent by weight. The optimum amount of ester which is added to thefuel oil will depend to some extent on the nature of the fuel oil andthe lowest temperature at which the oil will be used.

The fuel oil compositions of the present invention can be prepared bydissolving the ester additive directly in the fuel. Special equipment isnot required and conventional liquid mixing or blending equipment may beused. The ester additive may, on the other hand, be dissolved in asuitable solvent to form an additive concentrate. This additiveconcentrate may then be used to prepare the fuel oil composition of thisinvention. The additive concentrate may contain up to 50 percent byWeight of the ester additive. In either case, that is whether the esteris added (a) directly to the fuel or (b) as an additive concentrate, thefinal effective concentration of additive in the fuel oil will be withinthe ranges disclosed above.

In order to show the unobvious improvement in cold flow in fuelcompositions of this invention, the fuel oil compositions were evaluatedusing the Enjay Fluidity Test. The Enjay Fluidity Test measures the flowcharacteristics of fuel oils through a narrow orifice. The procedure andtest equipment are fully described in Enjays brochue ELD-48439. Thecontents of that brochure are incorporated by reference as part of thisspecification. Briefly, the test involves measuring the amount of fueloil which flows through an orifice in a given time at a giventemperature. The testing device consists of a twocompartment cylinderconnected by means of a capillary tube /2 inch long and 2.25 mm. insidediameter. Each chamber is calibrated. Forty milliliters of the fuel oilto be tested are placed in one chamber of the cylinder; the cylinder iscapped, inverted so that the fuel will not run into the other chamber,and placed in a bath set at the desired temperature for two hours. Atthe end of this time, the cylinder is inverted so that the cooled fuelnow can run through the capillary tube into the second chamber. The testapparatus is kept in the cooling bath while the fuel is allowed to flowfor three minutes. At this point, the amount of fuel which has flowedthrough is measured. It is reported as percent recovery of total fuelsample used. The higher the percent of fuel which passes through, thebetter cold-flow the fuel composition has. Thus, for example if 20 ml.of fuel oil flows from the first chamber to the second chamber, theEnjay Fluidity Recovery is 50 percent.

Following are the Enjay Fluidity results obtained in running a series offuels. The ester additives were prepared using the procedures disclosedabove. All the tests were conducted at 25 F.

TABLE I.ENJAY FLUIDITY 1 The base fuel used was Mobil Grade No. 2 fueloil. 2 Average of two runs.

The data in Table I clearly indicates the effectiveness of the sorbideand sorbitan palmitate esters as cold flow improvers. The base fuelWithout any additive would not flow through the capillary tube in theEnjay test apparatus. Addition of from 0.06 to 0.1% by weight of eitherthe sorbide or sorbitan palmitate improves this cold flow characteristicof the fuel to the point where up to 93% of the fuel did flow throughthe capillary tube at 25 F.

Comparable improvement in cold flow is obtained when analogous anhydromannitol, anhydrodulcitol, anhydroxylitol esters and the like are usedin place of the sorbide or sorbitan palmitates.

A series of fuel compositions were also run to show the criticality ofthe C alkyl moiety in the esters of this invention. Again all tests weremade at -2S F. using the Enjay Fluidity Test described above. The dataare presented in Table II below.

1 Base fuel is the same as that used in fuels of Table I; concentrationof additive in each case is 0.1 weight percent.

The data in Table II clearly illustrates the unexpected superiority ascold flow improvers of the C alkide and alkitan esters over homologous CC and C esters. This increased potency is surprising and whollyunexpected. Thus, when sorbide monopalmitate is added to fuel oil, 83percent recovery at 25 F. is effected. Using the same amount of theanalogous C or C ester, that is, the monomyristate or monostearate,there is a marked decrease in cold flow activity as indicated by thelower percent recovery. It is readily apparent then that the alkylportion of the anhydroalkitol esters useful in this invention must have16 carbon atoms in order that the fuel oil compositions containing theesters have substantially improved cold flow characteristics.

In addition to the anhydroalkitol esters, the fuel oils of the presentinvention may contain other additives. Thus, the fuel oil may containcombustion improvers such as amyl nitrate, acetoneperoxide, and thelike; smoke reducers such as overbased calcium sulfonates,methylcyclopentadienyl manganese tricarbonyl, and the like; corrosioninhibitors such as linoleic acid dimer and the like; antioxidants suchas 2,6 di tert butylphenol, N,N di sec butyl p phenyline diamine and thelike: metal deactivators such as N,N' disalycilidine,

1,2-propane diamine and the like. Any or all of these types of additivesmay be present in the fuel oil provided that they do not inhibit thecold flow activity of the anhydroalkitol esters.

The compositions of our invention are fully described in the disclosurepresented above. The specification includes data which points out andconfirms the unobvious and unexpected nature of this invention. It isnot intended that the invention be limited except within the lawfulscope of the following claims.

We claim:

1. A fuel oil having improved cold flow characteristics containing from0.04 to about 0.5 percent by weight of an ester of palmitic acid and ananhydroalkitol, said anhydroalkitol having from 5 to 7 carbon atoms.

2. The fuel oil of claim 1 wherein said fuel oil contains from about0.06 to about 0.1 percent by weight of said ester.

3. The fuel oil of claim 1 wherein the ester is selected from the groupconsisting of sorbitan monopalmitate, sorbitan dipalmitate, sorbidemonopalmitate, sorbide dipalmitate and mixtures thereof.

4. The fuel oil of claim 3 wherein the ester is sorbitan palmitate.

5. The fuel oil of claim 3 wherein the ester is sorbitan dipalmitate.

6. The fuel oil of claim 3 wherein the ester is sorbide monopalmitate.

7. The fuel oil of claim 3 wherein the ester is sorbide dipalmitate.

References Cited UNITED STATES PATENTS 2,527,889 10/1950 Moore et al.4466 2,548,347 4/1951 Caron et al. 4466 2,398,193 4/1946 Sharp 25233.42,322,820 6/1943 Brown 260-333 DANIEL E. WYMAN, Primary Examiner Y. H.SMITH, Assistant Examiner US. Cl. X.R.

